class Nod {
  protected:
    Nod *fStang, *fDrept;
    static long double x;
  public:
    Nod();
    ~Nod();

    virtual long double calcul()=0;
    virtual char *derivare()=0;
    virtual long double calculDerivare()=0;
    virtual char *toString()=0;

    Nod *getFStang();
    void setFStang(Nod *x);
    Nod *getFDrept();
    void setFDrept(Nod *x);

    static void setX(long double X);
    static long double getX();
};
    
